Magneto optical disc

Abstract

A protective coating made of resin, preferably a radiation curable resin containing fluoroplastic fine particles having a low surface energy is provided in the form of the uppermost layer facing a magnetic head, thereby improving the frictional properties and durability of a magneto-optical disc that is used with a magnetic field modulation system in which the magnetic head comes in constant contact therewith.

We claim: 
     
       1. A magnetic field modulation type of magneto-optical disc, comprising: a substrate;   a recording layer formed on said substrate;   a protecting coating formed on said recording layer; and   said protecting coating is a layer of a resin containing fine particles of polytetrafluoroethylene having a molecular weight of 600 to 200,000, said protecting coating having a thickness of 1 to 30 μm and further including a fluorine-containing nonionic surfactant in accordance with the following formula: ##STR5##  wherein: Rf designates a perfluoroalkyl group having 4 to 12 carbon atoms; L 1  denotes a sulfonyl group; L 2  denotes a carbonyl or carbonyloxy group; R 1  denotes a hydrogen atom or an alkyl group; R 2  denotes an alkyl group; and m denotes a positive integer of 1 to 20.   
     
     
       2. A magneto-optical disc as recited in claim 1, wherein said fine particles have a mean particle diameter of 0.1 to 10 μm. 
     
     
       3. A magneto-optical disc as recited in claim 1, wherein said protecting coating contains 2 to 40% by weight of said fine particles. 
     
     
       4. A magneto-optical disc as recited in claim 1, wherein said resin containing said fine particles is a radiation curing resin. 
     
     
       5. A magneto-optical disc as recited in claim 1, wherein said nonionic surfactant contains a component having a molecular weight of substantially no greater than 20,000. 
     
     
       6. A magneto-optical disc as recited in claim 1, wherein the amount of said nonionic surfactant in said protecting coating is 0.1 to 5% by weight.